The present invention relates to selectors for rectangular sheets, in particular, banknotes which can be introduced into machines which are automatically capable of recognizing them, validating them and processing them during a transaction.
This type of automatic machine, called a selector hereinafter, is limited at this time, in general, to the proper processing of banknotes as well as other valuable documents, such as certain types of checks. These automatic machines may also find application in the future in machines designed to process other paper documents such as deeds, bills of exchange, discount bills, or other documents used in financial transactions, as well as to interpret orders issued to effect such transactions or operations.
The selector comprises a bill conveying device located at an input channel. This conveying device is generally triggered by a system detecting the introduction of the bill in an introduction orifice. This conveying device may include one or several rollers or a central belt. Authentication tests are generally conducted in a second section of the selector, located after the input channel.
For the bill to be processed correctly in this second section, the conveying device conveys the bill into the second section of the selector. For this verification procedure to be carried out correctly, it is necessary for the bill to arrive in a precisely aligned fashion. This alignment is evaluated against a reference surface against which one edge of the bill comes to lie. The recognition and authentication device located in the second section of the selector is able to analyze the grain of the paper, its watermark, its color and the imprinted images. If the left edge of the bill does not coincide with the reference surface, the conveying device feeds the bill in a faulty position and the recognition device is not able to recognize or to validate the bill as it attempts to compare the bill with reference models whose characteristics were previously stored in memory. It may in that case reject it erroneously.
In general, where the selector accepts several types and therefore several sizes of bills, the introduction orifice is generally wider than the bill introduced by the user. As a result, a risk generally exists that the bill will be misaligned with respect to the reference surface, resulting in the inconvenience described above.
In known systems, different devices are found which make it possible to align the bills correctly after they have been introduced into the machine- These devices include in particular one or several rollers which convey the bill. These rollers can be identical to those of the conveying device mentioned earlier and are themselves driven by a motor which is started up when one or several detection systems, comprising for example a transmitter and a receiver of a light ray placed across the introduction orifice, detect the bill which the user is in the process of introducing. The rotational axis of these rollers is in principle perpendicular to the direction of the reference edge; however, some of these rollers will be able to rotate around an axis which is slightly offset from that direction so as to press the bill against the reference edge. Patent document UK-A-2,063,830 describes an example of such a device.
In another conveying system, called a central-belt conveying system, a single conveying means causes the bill to advance without attempting to align it against the reference surface. This system can also be used to convey the bill into the second section of the selector. In this case, the bill will be conveyed so that the area of said bill which is most frequently folded when it is kept in a billfold lies on this belt as this area is always more or less damaged and does not lend itself well to paper-grain recognition operations and other optical authentication tests which are carried out in this second section of the selector.
In the conveying systems which have just been described, there does not exist any device verifying whether the alignment is indeed correct. Since the alignment devices are not perfect, it is sometimes possible that the bills are not aligned properly. This leads to errors in the results indicated by the authentication device. Consequently, not only authentic bills may be rejected, but also, albeit not as easily, counterfeit bills may be accepted by an automatic machine.